Water-soluble nonstoichiometric polyelectrolyte complexes of modified chitosan

A modified polysaccharide that, in each deacetylated unit, carries a functional secondary amino group and a quaternized amino group that provides a positive charge and solubility to the polymer throughout the pH range is prepared by the alkylation of primary amino groups of chitosan with glycidyltrimethylammonium chloride. The mixing of modified chitosan solutions with solutions of polystyrenesulfonate or polymethacrylate anions in neutral solutions gives rise to negatively charged nonstoichiometric polyelectrolyte complexes soluble and stable under physiological conditions. The effects of pH, ionic strength, the degree of polymerization, the nature of the lyophilizing polyanion, and the charge-to-charge ratio of components on the boundaries of existence of soluble complexes are ascertained. The collected experimental data may serve as a basis for designing biocompatible and biodegradable means useful for the delivery of genetic material and drugs to living cells.     

Water-soluble modified chitosan and its interaction with a polystyrenesulfonate anion

The selective alkylation of primary amino groups of polysaccharide is conducted through the interaction of chitosan with glycidyltrimethylammonium chloride with introduction of the quaternized amino group into every alkylated unit, thereby ensuring a positive charge and solubility of the polymer over the entire pH range. The structure of the modified chitosan is studied via FTIR spectroscopy and ¹³C and ¹H NMR measurements. On the basis of the potentiometric titration of solutions of the parent polysaccharide, its modified derivative, and their mixtures with the polystyrenesulfonate anion, as well as ζ-potential measurements and turbidimetric titration of polymer mixtures, it is demonstrated that the secondary amino group of the complexed modified chitosan can be protonated in weakly acidic solutions. This behavior is of particular importance for the design of biocompatible and biodegradable vehicles suitable for the delivery of genetic material and drugs to cells.     

Studies of the association of chitosan and alkylated chitosan with oppositely charged sodium dodecyl sulfate

Cationic biopolymer chitosan has many applications in food, cosmetic and pharmaceutical industries. Grafting alkylated chains on its backbone can hydrophobically modify this water-soluble polymer.This paper concerns unmodified chitosan, alkylated chitosan and their interactions with a model anionic surfactant, sodium dodecyl sulfate (SDS). The solvent is pH 4 acetic acid solution. The purpose of this study is to highlight the hydrophobicity brought by the alkylated chains by comparing surface tension measurements and rheological properties of hydrophobically modified polymer (HMP) and chitosan solutions at 25 °C.Interactions of chitosan and HMP with surfactant have also been investigated giving information about surface activity and electrical conductivity of such systems. It results that alkylated chitosan/SDS system is more surface active than chitosan/SDS and it offers new potential applications in pharmaceutical and cosmetic fields because of the formation of amphiphilic complexes.     

Nonstoichiometric polyelectrolyte complexes of chitosan soluble in neutral solutions

The technique of preparing nonstoichiometric polyelectrolyte complexes of chitosan soluble in neutral solutions is developed. Chitosan complexes soluble in neutral solutions and meeting the behavioral criteria of water-soluble nonstoichiometric polyelectrolyte complexes are prepared via mixing of strongly acidic solutions of chitosan and polystyrenesulfonate anions taken in a nonequimolar charge-charge ratio and subsequent neutralization of the products by a solution of alkali. Thus, the region of existence of soluble complexes narrows with a decrease in the length of the host polyanion up to its full degeneration in the case of oligomeric anions. The critical concentration of a salt that brings about phase separation decreases with an increase in the relative content of the guest chitosan in a mixture and depends on the ratio of chain lengths of polymer components.     

Soluble–insoluble polyelectrolyte complex of quaternized chitosan with DIVEMA (pyran copolymer)

To endow chitosan with solubility in the whole pH-range without loss of functionality of the amino groups, the cationic polysaccharide was exhaustively alkylated yielding N-[(2-hydroxy-3-trimethylammonium) propyl]chitosan chloride (QCht). Each alkylated unit of QCht contained both quaternary amino group and secondary amino group. Recently we demonstrated that QCht forms with nucleic acids of soluble polyelectrolyte complexes stable at physiological conditions and capable of cell transfection in vitro. In the current work, the anionic counterpart of QCht was hydrolyzed copolymer of divinyl ether and maleic anhydride (DIVEMA) which is known to possess some anti-tumor and immune stimulating activity and use as a drug carrier in anti-tumor drug delivery systems. According to the potentiometry data and ζ-potential measurements, almost all carboxylic groups of DIVEMA were able to form ion pairs with QCht. In aqueous and water–salt solutions, formation of either soluble or insoluble complexes was controlled by pH, ionic strength, a ratio of the oppositely charged groups, and degree of polymerization of the chains following general rules revealed on studying polyelectrolyte complexes of polycarboxylic acids. These findings evidence plausible advantages of the complex formation as the non-covalent modification that imparts to both polyelectrolytes of the ability for reversible soluble–insoluble transformation under enzyme-friendly conditions.     

Preparation and characterization of nanoparticles formed by chitosan-caseinate interactions

Intermacromolecular complexation between chitosan and sodium caseinate in aqueous solutions was studied as a function of pH (3–6.5), using absorbance measurements (at 600 nm), dynamic light scattering (DLS), and transmission electron microscopy (TEM). The chitosan–caseinate complexes formed were stable and soluble in the pH range 4.8–6.0. In this pH range, the biopolymers had opposite charges. At higher concentrations of chitosan (0.15 wt%), the soluble complexes associated to form larger particles. DLS data showed that, between pH 4.8 and 6.0, the particles formed by the complexation of chitosan and caseinate had sizes between 250 and 350 nm and these nanoparticles were visualized using negative staining TEM. Above pH 6.0, the nanoparticles associated to form larger particles, causing phase separation. Addition of NaCl increased the particle size. The pH dependence of the zeta potential of the mixture solutions was appreciably different from that of the pure protein and pure chitosan solutions.     

Efficient Transfection via an Unexpected Mechanism by Near Neutral Polypiperazines with Tailored Response to Endosomal pH

Cationic pH-responsive polymers promise to overcome critical challenges in cellular delivery. Ideally, the polymers become selectively charged along the endosomal pathway disturbing only the local membrane and avoiding unintended interactions or cytotoxic side effects at physiological conditions. Polypiperazines represent a novel, hydrophilic class of pH-responsive polymers whose response can be tuned within the relevant pH range (5–7.4). The authors discovered that the polypiperazines are effectively binding plasmid DNA (pDNA) and demonstrate high efficiency in transfection. By design of experiments (DoE), a wide parameter space (pDNA and polymer concentration) is screened to identify the range of effective concentrations for transfection. An isopropyl modified polypiperazine is highly efficient over a wide range of concentrations outperforming linear polyethylenimine (l-PEI, 25 kDa) in regions of low N*/P ratios. A quantitative polymerase chain reaction (qPCR) surprisingly revealed that the pDNA within the piperazine-based polyplexes can be amplified in contrast to polyplexes based on l-PEI. The pDNA must therefore be more accessible and bound differently than for other known transfection polymers. Considering the various opportunities to further optimize their structure, polypiperazines represent a promising platform for designing effective soluble polymeric vectors, which are charge-neutral at physiological conditions.     

Synthesis and characterization of folic acid‐modified carboxymethyl chitosan‐ursolic acid targeted nano‐drug carrier for the delivery of ursolic acid and 10‐hydroxycamptothecin

Carboxymethyl chitosan (CMCS), as a water‐soluble, biocompatible, and biodegradable polymer, is an excellent carrier for a sustained drug delivery system. In this study, a amphiphilic carboxymethyl chitosan‐ursolic acid nano‐drug carrier modified by folic acid (FPCU) were prepared, and then the nano‐drug carrier wrapped another anticancer drug 10‐hydroxycamptothecin were self‐assembled into nanoparticles (FPCU/HCPT NPs). The FPCU/HCPT NPs had a suitable size, high drug loading efficiency of ursolic acid (6.4%) and 10‐hydroxycamptothecin (14.1%). The drug release study in vitro indicated that the nanoparticles have obviously sustained effect and pH sensitive behaviors, the drug release amount was higher at pH 5.5 than at pH 7.4. in vitro and in vivo study showed that the nanoparticles displayed a high antitumor efficiency to tumor cells compared with free drug. The nano delivery system as a carrier for ursolic acid (UA) and 10‐hydroxycamptothecin (HCPT) has good application prospects in cancer treatment.     

Odd-even effect of repeating aminoethylene units in the side chain of N-substituted polyaspartamides on gene transfection profiles

A series of the N-substituted polyaspartamides possessing repeating aminoethylene units in the side chain was prepared in this study to identify polyplexes with effective endosomal escape and low cytotoxicity. All cationic N-substituted polyaspartamides showed appreciably lower cytotoxicity than that of commercial transfection reagents. Interestingly, a distinctive odd-even effect of the repeating aminoethylene units in the polymer side chain on the efficiencies of endosomal escape and transfection to several cell lines was observed. The polyplexes from the polymers with an even number of repeating aminoethylene units (PA-Es) achieved an order of magnitude higher transfection efficiency, without marked cytotoxicity, than those of the polymers with an odd number of repeating aminoethylene units (PA-Os). This odd-even effect agreed well with the buffering capacity of these polymers as well as their capability to disrupt membrane integrity selectively at endosomal pH, leading to highly effective endosomal escape of the PA-E polyplexes. Furthermore, the formation of a polyvalent charged array with precise spacing between protonated amino groups in the polymer side chain was shown to be essential for effective disruption of the endosomal membrane, thus facilitating transport of the polyplex into the cytoplasm. These data provide useful knowledge for designing polycations to construct safe and efficient nonviral gene carriers.     

Interactions between chitosan-modified particles and mucin-coated surfaces

Lipid-based particles (Cubosome particles) were surface-modified by chitosan and the ratio between particles and chitosan was optimized to minimize the free chitosan concentration in the dispersion. The modified particles were characterized by electrophoretic measurements and the pH dependence of the zeta potential could be directly related to the protonation of chitosan. Interaction between the modified particles and mucin-coated silica surfaces were subsequently investigated in situ by ellipsometry to assess the mucoadhesive properties at physiologically relevant conditions. The result showed that a substantial amount of modified particles was adsorbed to mucin-coated silica surfaces at both pH 4 and pH 6, probably due to electrostatic interactions between amino groups in chitosan and negatively charged groups in mucin. Furthermore, the amount of bound particles decreased by less than 15% upon rinsing indicating relatively strong interactions. This investigation demonstrates that ellipsometry is a useful tool to study mucoadhesive properties of particles in the submicrometer range. Moreover, the novel chitosan-modified particles may be of interest for mucosal drug delivery applications.     

疏水化水溶性聚电解质的增粘作用

疏水化水溶性聚电解质是一种大分子主链或侧链上含有少量疏水基团的新型水溶性功能高分子材料,在水溶液中具有良好的耐盐耐温增粘作用和贮存稳定性。对该类聚电解质的特殊增粘作用及分子结构、聚合物浓度、无机盐、机械剪切作用、ｐＨ、温度、表面活性剂、老化时间及与其他疏水化水溶性聚合物作用等影响因素进行了综述。     

Preparation of water-soluble chitosan derivatives by modification of the polymer in vapors of monobasic acids

Sorption of vapors of monobasic acids and of vapors over their solutions of various concentrations by high-molecular-weight chitosan was studied. The dependence of the degree of the vapor sorption by the polymer on the acid solution concentration, chitosan molecular weight, and sorption temperature was determined. Watersoluble chitosan derivatives were obtained. The hydrodynamic properties of aqueous solutions of the modified samples were examined.     

Enhanced capacity of chitosan for transition-metal ions in sulphate-sulphuric acid solutions

Batch measurements have shown that the collection yields of chitosan for chromium(III), iron(III), nickel, copper(II), zinc and mercury(II) from sulphuric acid solutions are higher when the solutions contain ammonium sulphate, or when chitosan conditioned in ammonium sulphate is used, particularly at pH 3.0 and 5.0. The contrary is verified for the oxy-anions vanadate, chromate and molybdate. Manganese is never collected. At pH 1.0 no collection occurs. A procedure for recycling chromatographic columns includes fixation of Cu or Ni from a sulphate solution at pH 3-5 on sulphate-conditioned chitosan, and elution with 0.1M sulphuric acid/0.1M ammonium sulphate at pH 1.0; the presence of sulphate in the eluent obviates the detrimental effect of sulphuric acid on the next cycle. Sulphate is the favoured counter-ion of the chelated cations and its action produces shorter chromatographic bands. The interaction of sulphate with chitosan is discussed in terms of crystallinity and steric distribution of the protonated amino-groups in the polymer. Data on the new diethylaminohydroxypropylcellulose are included.     

壳聚糖包裹硅胶载体印迹牛血红蛋白的研究

用壳聚糖包裹的硅胶为载体, 利用壳聚糖表面的氨基与戊二醛结合, 在硅胶表面引入醛基, 固定模板蛋白(牛血红蛋白). 用溶胶-凝胶过程再次包裹固定蛋白质的载体, 洗去模板蛋白后, 得到具有选择性识别的牛血红蛋白分子印迹聚合物. 用红外光谱(IR)、扫描电子显微镜(SEM)和元素分析对聚合物进行了表征, 结果表明, 载体表面成功地接枝了分子印迹聚合物. 选择性吸附实验结果表明, 分子印迹聚合物具有良好的识别性能, 能实现水溶液中牛血红蛋白的富集.     

pH响应性可降解聚膦腈的合成和表征

采用亲核取代引入侧基再进一步修饰的方法合成了一种新型的可降解聚膦腈 ,红外光谱、氢核磁共振谱、元素分析证实了聚合物的化学组成 .体外降解实验表明当侧基修饰达一定比例时 ,聚合物降解行为表现出强烈的pH响应性 ,即聚合物的降解在pH6 0～ 7 4之间迅速加快 ,这类聚合物可望作为口服药物控释制剂的载体材料 .     

Nanocomposites based on modified chitosan and titanium oxide

The effect of primary amino groups and molecular mass of chitosan on the stability of suspensions based on nanoscale TiO₂ dispersions in acidic solutions of various concentrations at pH 2.5 was studied. In the case of chitosan prepared according to a commercialized process, the stability of TiO₂ suspensions was low and depended on the concentration of the polymer solution. Solutions of low-molecular-mass highly deacetylated chitosan prepared by solid-phase synthesis stabilized a dispersion of nanosized TiO₂ particles for a very long time. Nanocomposites based on a chitosan-PVA graft copolymer and TiO₂ were prepared, in which the initial filler dispersion is retained up to very high filling ratios. A potential use of these nanocomposites in photocatalytic processes is discussed. The results of this study can be used for refining engineering procedures and processes for the manufacture of new biocompatible, bioactive, and biodegradable functional composite materials based on chitosan and synthetic polymers.     

去质子化调控的肝素/壳聚糖抗凝血多层膜

本文研究了环境pH值变化对多层膜表面性能的影响, 并且评价了组装pH值与测试pH值的差异对多层膜血液相容性的影响.     

The study of the interaction between chitosan and 2,2-bis(hydroxymethyl)propionic acid during solid-phase synthesis

New polymer salts and N-acetylated chitosan derivatives are prepared in an extruder by the method of solid-phase synthesis via the interaction of chitosan and 2,2-bis(hydroxymethyl)propionic acid. The effect of the initial component ratio and temperature on the yield and structure of the target products is studied. Joint deformation of solid components at room temperature is found to cause the quantitative formation of salt bonds between carboxylic groups of the acid and amino groups of chitosan. At elevated temperatures of synthesis, the corresponding acetylated derivatives with a degree of substitution of amino groups varying from 0.16 to 0.43 are prepared. The relaxation and phase transitions in the polymer salts and acetylated chitosan derivatives and their sorptional activity are studied. The films prepared from aqueous solutions of the new salt modification of chitosan are characterized by a homogeneous structure and improved mechanical characteristics relative to those of the films based on chitosan acetates. An additional thermal treatment of the products of the solid-phase synthesis leads to the formation of crosslinked and water-swollen materials that can be used for the development of novel polymeric chitosan-based membranes and sorbents.     

Synthesis and Characterization of a Novel Soluble Diethoxy Phosphoryl Chitosan

A simple and efficient method for the preparation of a novel soluble chitosan derivative, diethoxy phosphoryl chitosan (PH‐chitosan), has been developed. Ph‐chitosan was characterized by elemental analysis, FT‐IR, NMR, ICP, XRD, TG and SEM, respectively. The chemical identity of PH‐chitosan was determined by FT‐IR and confirmed by NMR, and those results unequivocally demonstrated that diethoxy phosphoryl groups were grafted onto the amino and hydroxyl groups of chitosan. The results of XRD indicated that the crystalline structure of chitosan was destroyed due to the incorporation of diethoxy phosphoryl group resulting in loss of hydrogen bond. The analysis of TG demonstrated that PH‐chitosan was less thermal stable than chitosan. This simple synthetic method provided a new and available approach to prepare a soluble high molecule weight chitosan derivative.     

pH and temperature-sensitive N-isopropylacrylamide ampholytic networks incorporating L-lysine

Ampholytic polymer gels based on N-isopropylacrylamide (NIPA) and natural amino acid L-lysine were prepared by free radical polymerization in aqueous solutions. To make amino acids attachable to the polymer chain, the acrylic group was added to the epsilon-amino group of lysine to obtain N-epsilon-acrylic-lysine (Z). Finally, a new temperature- and pH-sensitive (NIPA-Z) hydrogel was obtained. The presence of amino and carboxylic groups of amino acids gave us a possibility to control the amount and sign of the excessive charge on the polymeric network with respect to pH. The swelling behavior of the NIPA-Z hydrogels with respect to the amount of Z (0-4%), temperature, and pH was investigated. Temperature and pH were changed in the ranges of 20-50 degrees C and 2-12, respectively. To eliminate the influence of ionic strength on the swelling behavior, this parameter was kept constant in all experiments. It was found that the pH dependence of the degree of swelling for the NIPA-Z gels, measured at constant temperature, exhibits a minimum. Such a minimum was seen for the ampholyte networks with independent acidic and basic groups attached to the polymer chains. For the NIPA-Z gels, the minimum was wide, and the pH range over which it was spread corresponded well to the pH distribution of the zwitterions. The way the gel volume changed with an increase in temperature depends on the amino acid amount. It is initially discontinuous and turns to the continuous one for the higher percentage of amino acid. The temperature dependence of the swelling process obtained for different pH values clearly shows that for the pH region where the zwitterions dominate, the polymer networks collapse more efficiently.